Andy Ruiz Jr caused one of the greatest upsets in the history of boxing on Saturday night when he stopped Anthony Joshua in the seventh round at Madison Square Garden.

The 29-year-old became the first Mexican-American heavyweight world champion, claiming the IBF, WBO and WBA belts held by the English fighter.

Ruiz Jr was a massive under going into the bout. His pudgy appearance compared to the more chiseled physique of his opponent exacerbated a presumption that it would be an easy night's work for Joshua in New York.

Ruiz Jr only discovered a month before the fight that he would be facing Joshua. Jarrell Miller, who was originally scheduled to be Joshua's opponent, tested positive for a banned substance in the build-up.

Speaking ahead of last night's fight, Joshua's promoter Eddie Hearn explained that Ruiz Jr only came to his attention when he sent him a message via Instagram.

"Once the three positive drugs tests came in, we searched for a new opponent," Hearn said on Thursday.

Advertisement

I wasn't under any instructions, it was a case of whoever you want.

Someone sent me a direct message on Instagram: 'I'm fighting Saturday. Give me this fight, I will fight harder than any of the names you've mentioned, I will give you a better fight and I will beat Anthony Joshua'.

OK, that got my attention. We had a look, we saw him deal with and stop Alexander Dimitrenko on Fox and the discussions continued.

I've found a man who had a burning desire to create history, to create a legacy, and become the first ever Mexican world heavyweight champion.

Last night's victory earned Ruiz Jr a purse of around $7m. The inevitable rematch against Joshua should make him even more.